Flow amplifying poppet valves typically include a poppet having a reduced diameter end seated against a valve seat in the valve housing. Fluid flow from an inlet port through the valve to an outlet port is controlled by controllably moving the poppet off the seat. A basic type of poppet valve has a throttling slot through the poppet to communicate the inlet port pressure to a control chamber at the backside of the poppet. The fluid pressure in the control chamber exerts a closing force on the poppet holding it against the valve seat. A spring is also generally used to hold the valve element against the valve seat when the inlet, control and outlet pressures are all equal.
Controlling the opening position of the poppet is normally accomplished by communicating the control chamber with the outlet port through a variable regulating orifice of a pilot valve. The variable regulating orifice is normally closed so that fluid pressure in the control chamber equals the inlet pressure and the poppet valve element is urged against the seat by the pressure in the control chamber. Opening of the poppet is achieved by controllably opening the variable regulating orifice to communicate the control chamber with the outlet port. This creates a pressure drop through the throttling slot in the poppet such that the inlet pressure urges the valve element off the valve seat as the control pressure drops below the balance pressure. The degree of opening of the poppet is subsequently controlled by controlling the flow through the variable regulating orifice of the pilot valve to regulate the flow through the throttling slot.
One of the problems encountered with the known flow amplifying poppet valves is caused by the flow forces acting on the pilot valve and produce undesirable or uncontrollable results particularly when the pilot valve is a proportional solenoid valve. Even though the pilot flow through the pilot valve is relatively small, the flow forces can be relatively large due to large pressure drops between the control chamber and the outlet port. The flow forces in many cases require the use of a larger more powerful solenoid to move the pilot valve against the flow forces.
The present invention is directed to overcoming one or more of the disadvantages or problems as set forth above.